1. Field of Invention
The present invention relates to a method of fast image matching.
2. Description of Related Art
An image matching technique relates to determining the similarity between images by a similarity pointer. A general image matching technique relates to comparing two pieces of images, wherein one piece is a template image, and the other piece is a testing image. The comparison is intended to find a best match relation between the two images. A most commonly used image matching technique is Normalized Cross Correlation (NCC), as represented by the following equation. Features of NCC are insensitivity to a light ray change and great resistance to noise interference.
  r  =                    ∑                  i          =          1                m            ⁢                        ∑                      j            =            1                    n                ⁢                              (                                          W                ⁡                                  (                                      i                    ,                    j                                    )                                            -                              W                _                                      )                    ⁢                      (                                          G                ⁡                                  (                                      i                    ,                    j                                    )                                            -                              G                _                                      )                                                        ∑                      i            =            1                    m                ⁢                              ∑                          j              =              1                        n                    ⁢                                                    (                                                      W                    ⁡                                          (                                              i                        ,                        j                                            )                                                        -                                      W                    _                                                  )                            2                        ⁢                                          ∑                                  i                  =                  1                                m                            ⁢                                                ∑                                      j                    =                    1                                    n                                ⁢                                                      (                                                                  G                        ⁡                                                  (                                                      i                            ,                            j                                                    )                                                                    -                                              G                        _                                                              )                                    2                                                                        
wherein, r=similarity
m, n=size of target windows
W(i, j), G(i, j)=gray-scale values of target windows and search windows
 W, G=gray-scale averages of target windows and search windows
The general image matching technique relates to comparing template images in the range from 0 to 360 degrees with a testing image, in order to calculate a tilt angle of an object in the testing image, as illustrated in FIG. 1. This method is also called a brute force which is time-consuming and involves a great deal of data.
Hence, the existing image matching method described above apparently requires a further improvement. To solve the problems above, those of skills in the related fields are seeking for solutions by all efforts, which is in vain that no suitable method has been developed and completed so far. Thus, how to implement faster image matching becomes indeed one of those important research and development topics at present, as well as an improvement target required in all related fields.